1. Field of the Invention
This invention relates to a liquid treating apparatus carrying out an antibacterial treatment against disease bacteria or fungi and protozoan present in a liquid and a treatment for elimination of impurities.
2. Description of the Related Art
Crop growth using a nutrient solution such as hydroponics or rockwool growth systems has recently been conspicuous in the field of agriculture. With this, crops have adversely been affected by disease bacteria in an increasing number of cases. The disease bacteria invade from used raw water or from environment of such growth systems and propagate in a recirculated liquid used in the systems. Further, problems have arisen of adverse effects of bacteria and filamentous fungi on human bodies. The adverse effects include hospital infection due to legionella bacteria propagated in raw practical use water or methicillin-resistant staphylococcus aureus (MRSA) and food poisoning due to enterohemorrhagic escherichia O-157 or staphylococcus aureus. In view of the foregoing problems, the prior art has proposed bactericidal methods using chlorine chemicals, organic chemicals or the like, sterilizing methods using a sand filter, nutrient solution sterilizing methods using a bactericidal system by the use of ozone or ultraviolet lamps.
However, the above-noted bactericidal methods using chlorine chemicals are quick-acting but not persistent in the effect. Accordingly, the chlorine chemicals need to be used continuously but this increases the costs. Further, the chlorine chemicals have the defect of accelerating production of carcinogenic trihalometane. In the bactericidal methods using organic chemicals, drainage of the re-circulated liquid containing the organic chemicals has an enormous influence upon the environment. Further, in physical methods of adsorbing bacteria using various types of filter media, the accuracy in the filtration is insufficient and currently ineffective. Moreover, equipment carrying out the methods is large in size. Accordingly, an initial cost is increased. Additionally, the methods using ozonized water are not persistent in the effect and result in an increase in the cost, too. Additionally, in the bactericidal methods using ozone or ultraviolet lamps, control of nutrient solution becomes difficult since the ozone or ultraviolet lamps induce deposition of a slight amount of element.